This is my air-to-air solar panel that I built myself. It is 90″ tall and 16′ wide. It uses aluminum downspout tubing as the heating method. Air is pulled from a window opening, down a manifold area, through the tubing (which is painted flat black), into the hot manifold end, and into a second window duct. This duct has a fan on it and a thermal switch to control the fan automatically. It has been running since Feb 2010.
Inspiration for this project came from similar ones built by guys at www.builditsolar.com where they have this and many other solar projects.
I’m currently researching Evacuated Tube solar panels to tie into my floor heat tubing as an alternative to an electric or wood or fossil fuel boiler.
I forgot to take pictures of the initial building of it, so I’ll show the final building, and installation onto the shop.
I had gotten some surplus pieces of polycarbonate, 1/8″ thick and ~45″ x 48″ for ~$5 a piece if memory serves me correctly. Full sheets of 48×96″ sheets are expensive, my research showed about $100+ per piece.
I made the frame out of 2×6 lumber, sheeted the back with 7/16″ plywood, and then sheeted the interior with 1″ foil foam from Lowe’s. I used 1×6’s to make the manifold areas on each end, and then fitted in the aluminum eavesdrop tubing. All of the tubing was painted flat black before assembly, and the inside was also all painted black. My wife did a lot of the painting on this, which was awesome, as I hate painting!
Then we also painted the back white to blend with the shop better, and give it a nice finished appearance.
After that, we loaded it on the trailer for a trip to the shop.
Here it is on the trailer and then our work getting it ready for installation:
So now it’s time to attach the poly carbonate sheets. I got some foam tape, which I applied first, then the PC sheet, then used a vinyl 1×2 with screws to hold the PC to the frame. This allows a bit of give for thermal expansion, and an easy way to remove a sheet if repairs are needed later. I left the protective paper on the sheets for now so I wouldn’t scratch it during the main install.
I also lag screwed some vertical 2×4’s to the outside wall, tying into the horizontal perlins of the wall, and to space the panel out so it doesn’t hit the ribs of the sheetmetal.
Now it’s time to try to install this. This is way before the knuckleboom project, so I needed to be a bit creative to install this. There was a significant amount of snow on the ground, and even after snow blowing, there was no way I was going to risk getting stuck with the forklift! Fortunately, I had recently bought a big flatbed truck, 1951 International, and the height of the flatbed was only a few inches below where I wanted the solar panel to install. So using the cherry picker, I lifted it up onto the flatbed, and made some braces.
There was still a few inches between the panel and the wall, and a gap between the flatbed and the wall, so I used some long 2×4’s to cantilever the panel off the flatbed out to the wall. From there it needed to go up a few inches, so we used some ratchet straps and 2×4’s inside the windows to lift and pull it in.
Now that the panel was physically installed, I could add the heat ducts from Lowes to connect from the panel to the windows. I also had a 6″ fan with 120VAC that I installed inside the round ducting inside on the exhause (hot) side, and then put a thermal switch at the top of the exhaust (hot) side. The thermal switch is normally open, and closes at 90 degrees F, which then turns on the fan. During the summer, I just unplug the cord, otherwise the fan would just run whenever the temperatures are over 90F. These switches are available at any furnace shop, as they’re used on gas furnaces. Should be $5-10 for them.
Now, if I left it like that, I’d have a lot of heat loss both on the intake and especially on the exhaust, so I need to insulate and frame those ducts in and also to protect them from weather.
Here’s a youtube video of the CAD model that I generated and simulates the build process and installation process onto the building.
Plans: solar-panel plans
So now it’s finished. The air is pulled in from the left side, is drawn through the black pipes from left to right, and warmed as it goes. The thermal switch is on the right, at the top, and activates the fan to pull the air through.
As long as the sun is shining during the day, it’s making heat. It faces due south, and generally turns on between 9am and 10am, and shuts off around 3pm, mostly due to some trees that block it at that angle. Because the sun angles are low in the south sky during the winter, it works well. As it transitions into summer, the sun is much higher in the sky, and then the roof overhang blocks the sun, so that prevents it from getting too hot inside the panel during summer.
It doesn’t seem to matter how cold it is outside, it will output hot air as long as the sun is shining. The proof is in the pudding, as over the years it has kept the shop at 25-40F even with outside temperatures ranging from 20 to -20F. This is currently the only source of heat in the shop that runs consistently. The total volume of air is huge, 55′ x 50′ x16′. I believe I spent around $400 in materials and paint. Electricity cost is pretty minimal compared to everything else that’s drawing power in the shop. Almost free heat, and good for the environment, that’s a win-win in my book!
Long term plans are to add glass evacuated tube solar collectors on the roof, and tie them into the radiant heat piping that is in the concrete of the floor. That’s where the knuckleboom crane project will be useful: lifting panels up to the roof for installation. In the meantime, I’ve been working on quoting available products, and learning as much as I can for the next phase.